1. Field of the Invention
This invention relates to apparatus for moving a carriage or the like in one direction over a predetermined distance at a substantially uniform velocity and for returning the carriage at a varying velocity, which apparatus serves preferably to intermittently advance a plastic film web relative to a welding or cutting device fixed to a frame or for cyclically advancing a welding device with a plastic film web moving at the same velocity. The apparatus comprises a lever, which is adapted to be pivotally oscillated by a drive and which by means of a first guide provided on and extending along said lever and a slider or roller cooperating with said guide imparts a motion to the carriage. The carriage is movable on tracks in a plane which is parallel to the plane in which the lever is pivotally movable. The slider or the bearing for the roller is mounted on a holder, which is guided for a displacement along a line constituting the base of an isosceles triangle, the sides of which are defined by the lever at the end positions of its pivotal movement.
2. Description of the Prior Art
Two similar apparatus are disclosed in German Patent Specification No. 32 34 227. These apparatus have so-called synchronizing cam mechanisms, which have proven highly satisfactory but have the disadvantage that they occupy a large space. The pivotally oscillatable levers for driving the carriage of this publication consist of two-armed levers having a driving arm which is provided with cam follower rollers, which embrace a cam rib that is formed on a rotating cam-wheel and from which the drive motion is derived.